The present invention relates to a disk drive adapted to access a recording medium such as a magnetic disk for recording and reproducing data thereon.
Referring to FIGS. 1 through 3, a conventional magnetic disk drive is described, that is designed for magnetic disks. Such a magnetic disk drive is disclosed in, for example, Japanese Patent Laid-open No. 9-91943. FIG. 1 shows the magnetic disk drive with a reception mechanism for receiving a magnetic disk and an ejection mechanism for ejecting it being omitted for clarity. A chassis 10 comprises side walls 10-1 on both sides thereof. All components and parts are mounted on a major surface of the chassis 10. A main printed wiring board 11 and a sub printed wiring board 20 are fixed by screws to the major surface of the chassis 10. For the main printed wiring board 11, two support members 10-2 (FIG. 2) are formed by cutting and rising a major plate of the chassis 10. The main printed wiring board 10 is fixed to the two support members 10-2 with screws 12.
A stepping motor 13 is attached to a rear wall 10-3 at a rear end of the chassis 10. An output shaft 13-1 of the stepping motor 13 penetrates through the rear wall 10-3. The free end of the output shaft 13-1 is rotatably supported by a shaft receptacle 10-4 formed by means of cutting and rising the major plate of the chassis 10. The output shaft 13-1 has threaded outer peripheral surface. A carriage mechanism 14 is provided with an arm 14-1 having a pin 14-2 embedded therein. The pin 14-2 engages with threads in the output shaft 13-1. Consequently, rotation of the output shaft 13-1 moves the carriage mechanism 14 in the same direction as the output shaft 13-1. The carriage mechanism 14 comprises magnetic heads mounted thereon to access the magnetic disk. The carriage mechanism 14 is for moving the magnetic heads in the radial direction of the magnetic disk.
The carriage mechanism 14 is provided with a bearing arm 14-3 having an U-shape on the opposite side as the arm 14-1. A guide bar 15 penetrates through the bearing arm 14-3. The guide bar 15 is held by a guide bar clamp 16. Consequently, the carriage mechanism 14 is guided by the guide bar 15 when it moves in association with the rotation of the output shaft 13-1. The guide bar clamp 16 is fixed by a screw to a support plate 10-4 (FIG. 2). The support plate 10-4 is formed by cutting and rising the major plate of the chassis 10 and projects upward through a hole formed in the main printed wiring board 11.
In FIG. 3, a motor 21 for rotation driving the magnetic disk and other necessary circuit components (not shown) are mounted on the sub printed wiring board 20 only on the upper surface thereof. To this end, the sub printed wiring board 20 is fixed by the screws 12 (FIG. 1) such that it nearly contacts the major plate of the chassis 10 at the position closer to a slot for the magnetic disk, i.e., to a front bezel.
Configuration of the motor 21 is described in brief. The motor 21 comprises a rotation shaft 21-1, a center metal 21-2, cores 21-3 for a stator, stator coils 21-4, a ring-shaped permanent magnet 21-5, and a circular casing 21-6 attached to the rotation shaft 21-1. The center metal 21-2 is cylindrical and is used as a bearing. Each of the cores 21-3 extends radially from the center. The stator coil 21-4 is wound about an end of the core 21-3. The permanent magnet 21-5 is provided such that it surrounds a series of cores 21-3. The casing 21-6 holds the permanent magnet 21-5. The permanent magnet 21-5 and the casing 21-6 rotate in cooperation with the rotation shaft 21-1. A reference numeral 21-7 depicts an index magnet. The cores 21-3 and the stator coils 21-4 serve as a stator for the motor 21. The permanent magnet 21-5 and the casing 21-6 serve as a rotor for the motor 21. A combination of such stator and rotor is disclosed in, for example, Japanese Patent Laid-open No. 9-91866 and is thus not described herein.
The casing 21-6 has a central cone with a closed top to have a trapezoid configuration in cross section. A flat portion 21-6a at the top of the casing 21-6 is integrally fixed with a disk table 21-8 that is made of plastic magnet. The flat portion 21-6a is provided with an arm 22 on a bottom surface thereof. A drive roller 23 is rotatably mounted on the arm 22. The flat portion 21-6a and the disk table 21-8 have a generally rectangular hole formed therein. The drive roller 23 passes through the holes and projects upward from the disk table 21-8. The magnetic disk contained in the magnetic disk drive is mounted on the disk table 21-8. The drive roller 23 is inserted in and engaged with a hole formed in a hub of the magnetic disk. Consequently, the magnetic disk is rotation driven in response to the rotation of the rotor. The disk table 21-8 is disclosed in, for example, Japanese Patent Laid-open No. 9-91814 and is not described in detail herein.
An eject plate 24 is incorporated over the motor 21 as the ejection mechanism for the magnetic disk. A disk holder unit 25 is also incorporated over the motor 21 as the reception mechanism for the magnetic disk. The eject plate 24 and the disk holder unit 25 are also disclosed in the above-mentioned Japanese Patent Laid-open No. 9-91814 or 9-91943. The chassis 10 is assembled with a cover plate 18 to protect the space inside the chassis 10.
Meanwhile, the motor 21 is incorporated inside, that is, on the major surface of the chassis 10 in the above-mentioned magnetic disk drive. Therefore, magnetic flux generated by the stator coil 21-4 and/or the permanent magnet 21-5 affects the magnetic head and exerts a bad influence on writing and reading of data. In addition, the motor 21 when incorporated inside the chassis 10 occupies a most space of a limited space on the major surface of the chassis 10. This significantly restricts the space for mounting other mechanisms.
In order to contend with the above-mentioned disadvantages, the disk table 21-8 may be separated from the motor 21. However, the chassis 10 then requires a large opening to expose the motor 21 on a back side of the chassis 10. This means reduction of the mechanical strength of the chassis 10.